Solution of polypyrrolidone in superheated water



to form fibers or filaments.

United States Patent 01 3,076,774 SOLUTION F POLYPYRROLIDONE IN SUPERHEATED WATER William B. Black and Howard G. Clark III, Decatur, Ala., assignors, by mesne assignments, to Monsanto Chem.- ical Company, a corporation of Delaware No Drawing. Filed Sept. 21, 1959, Ser. No. 841,044 9 Claims. (Cl. 26029.2)

This invention relates to new compositions of matter; more particularly, the invention relates to new compositions of matter comprising polypyrrolidone and a solvent thereof.

Polypyrrolidone possesses many excel-lent properties which make it desirable for utilization in the manufacture of end products, such as ribbons, films, fibers, filaments, rods, bristles, lacquers, coatings, shaped articles and the like. Polypyrrolidone can be converted into shaped articles in many ways. For example, it may be cast into films or forced through multi-hole spinnerettes Regardless of the end use to which the polypyrrolidone is to be put, it is generally more convenient and efficient to employ the polymer in a solution. This is well illustrated in textile industry where polypyrrolidone is employed in the formation of fibers and filaments, whichare manufactured by several methods of spinning, such as melt spinning, dry spinning and wet spinning.

In the melt spinning method, the polymer is heated to a high temperature until it becomes molten, and is thereafter forced through sand packs and the like, and thence through a spinnerette from whence it is extruded in filamentary form. This method has, however, many disadvantages, although it is widely used in the industry at the present time in the production of synthetic fibers and filaments. The high temperatures used in melt spinning require the exercise of extreme care in order to prevent the decomposition of the polymer. Furthermore, the hightemperatures also aflect the chemical and physical characteristics of the polymer and thereby re suit in a product of inferior quality. In addition to these disadvantages, it is extremely difficult to add to the molten polymer at such high temperatures compound such as dyes, anti-static agents, plasticizers and thelike.

In the dry spinning method of fiber formation, the polymer is dissolved in a suitable solvent and subsequently extruded from spinnerettes into a heated atmosphere in order to evaporate the solvent. Even this method, however, has its disadvantages, since during the period of time in which the solvent evaporates, considerable damage may be inflicted on the fibers because of the high heat necessary to bring about solvent evaporation. Another disadvantage of the dry spinning method, and of the melt spinning method also, is the added cost necessary to maintain such high temperatures needed to manufacture the desired end product.

The wet spinning method obviates many of the disadvantages of both melt spinning and dry spinning. In order to form filaments by the wet spinning method, the polymer is dissolved in a suitable solvent and extruded from a spinnerette into a coagulating bath capable of leaching the solvent from the fibers. Normally, this method may be carried out at temperatures much lower than either the melt spinning or dry spinning methods. If it is desired to use additives, such as dyes, antistatic agents, fire-retarding agents, plasticizers and the like, in the polymeric solution, they may be incorporated therein without the danger of decomposition or seriously aifecting the properties of the end product where the.

wet spinning method of filamentary formation is employed. It is much easier to introduce such additives into a solution than to introduce them into a molten composition. Then again, solutions are much easier to handle during processing, and in many cases may be stored for long periods of time without a change of physical and chemical properties. It is much easier to cast a film from a solution than to cast it from a molten composition. It is readily apparent, therefore, that solutions of polypyrrolidone possess many distinct advantages over molten compositions in the manufacture of end products.

Accordingly, it is a primary object of the present invention to provide new and useful compositions of matter comprising polypyrrolidone. It is a further object of the invention to provide a solution of polypyrrolidone which may be converted into shaped articles, such as ribbons, films, filaments, fibers, rods, bristles, and the like. It is still another object of the invention to pro vide a process for the preparation of a polypyrrolidone solution. Other objects and advantages of the invention Will be readily apparent from the description thereof which follows hereafter.

In general, the objects of the present invention are accomplished by dissolving polypyrollidone in superheated water.

When employing water in the practice of the present invention, it is based on the total weight of the solution mixture. As much as percent of water may be employed to attain the beneficial effects thereof and as low as 65 percent. However, as a practical matter, a solution containing from about 67 percent of water and as much as 90 percent water results in a solvent capable of dissolving polypyrrolidone to give a solution which is valuable for being shaped into articles, such as filaments, fibers, rods, bristles, filaments, coatings, etc.

It will be readily apparent to those skilled in the art that polypyrrolidone can be dissolved in the solvent of the present invention in widely varying concentrations. The concentration of any particular polymer in the solvent depends upon the nature of this polymer, and the temperature, which in turn affects the viscosity of the solution. When the solution is to be employed in the manufacture of fibers and filaments, as much as 35 per: cent of the polymer, based on the total weight of the solvent, may be dissolved in the solvent of this invention. While it is preferred to employ from 10 to 33 percent of the polymer, based on the total weight of the solution, when the solution is to be used in the preparation of fibers and filaments, it is understood that as little as 5 percent or less and more than 35 percent of polypyr rolidone may be dissolved in the solvent of this invention when the solution is to be used for other purposes, such as a coating or a lacquer and the like, or when lower or higher molecular weight polypyrrolidones are dissolved in the solvent.

The solvent of this invention readily dissolves polypyrrolidone within a wide range of temperature, depending on the nature of the polymer and the concentration thereof in the solvent. Although temperatures within a range of C. to C. are preferred as a practical matter in bringing about solution, temperatures as low as 120 C. and as high as C. may be employed to bring about this dissolution. The polymer is dissolved by heating with water in an autoclave capable of withstanding the pressure generated by the superheated Water. Heat may be supplied by pressurized steam, an oil bath or other conventional means.

If it is desired to produce shaped articles from the polypyrrolidone compositions of the present invention which have a modified appearance and modified properties, various agents to accomplish these efiects may be added to the polymer solution prior to fabrication of the articles without having any ill effects thereon. Such agents may be plasticizers, pigments, dyes, anti-static agents, fire-retarding agents, and the like.

Polypyrrolidone soluble in the solvent of this invention may be prepared by various processes. Generally, however, polymeric pyrrolidone is prepared by polymerizing 2-pyrrolidone in the presence of a catalyst or a catalyst and activator at a temperature in a range of 70 C. to 100 C. However, since the polymerization reaction proceeds well in a range of 20 C. to 70 (3., these temperatures are preferred in carrying out a polymerization procedure.

In the preparation of polypyrrolidone, a large number of known catalysts are available to catalyze the poiymerization. Among such catalysts, there may be named the alkali metals, namely, sodium, potassium and lithium, as well as the hydrides, hydroxides, oxides and salts of the alkali metals, that is, such salts as sodium, lithium and potassium pyrrolidone. Organic metallic compounds, preferably those which are strongly basic, may be used as catalysts, too. Examples of such compounds are lithium, potassium, and sodium alkyls and aryls of the alkali metals, such as sodium phenyl. Another suitable catalyst is sodium amide. The alkali hydrides, however, are the preferred catalysts since a distinct advantage is obtained by their use. Sodium hydride, for example, does not react in the polymerization mixture to form water, which, as is well known, has a deleterious effect on polymerization of pyrrolidone. Where water-forming catalysts, such as sodium hydroxide, are employed as a catalyst, all water of reaction must be removed from the reaction mixture by vacuum distillation or other means in order for polymerization to proceed at a reasonable rate. Generally, the catalysts may be employed in a range of 0.002 to 0.25 chemical equivalents based upon one mole of monomeric pyrrolidone in carrying out a polymerization reaction.

Although polypyrrolidone having acceptable properties can be prepared by using a catalyst alone, it is preferable to employ an activator in conjunction with any of the catalysts mentioned above, since the polymer prepared in the presence of both a catalyst and activator has greatly improved properties over polypyrrolidone prepared in the presence of a catalyst alone. Among the compounds which may be employed as activators, there may be named the acyl compounds, such as acetyl pyrrolidone, acetyl morpholone, and the like; lactones, such as gamma butyrolactone, and the like; alkyl esters of monoand dicarboxylic acids, such as ethyl acetate, ethyl oxalate, and the like; the esters of polyhydric alcohols, such as ethylene glycol diacetate and the like; and nitrogen dioxide and organic nitrites having the general formula:

wherein R is selected from the group consisting of alkyl groups containing 1 to carbon atoms, haloalkyl groups containing 2 to 10 carbon atoms, nitroalkyl groups containing 2 to 10 carbon atoms, aralkyl groups containing 7 to 10 carbon atoms, and alkoxyalkyl groups containing 3 to 12 carbon atoms. Among the nitrites falling into the general formula set out above, there are methyl nitrite, ethyl nitrite, n-propyl nitrite, iso-propyl nitrite, nbutyl nitrite, iso-butyl nitrite, amyl nitrite, iso-amyl nitrite, hexyl nitrite, heptyl nitrite, octyl nitrite, nonyl nitrite, decyl nitrite, and their isomeric forms, and the like; haloalkyl nitrites, such as 2,2,2-trichloroethyl nitrite, the dihaloalkyl nitrites, such as 2,2-dichloroethyl nitrite, 2,2- dichloropropyl nitrite, 2,2-dichlorobutyl nitrite, 2,2-dichloroamyl nitrite, 2,2-dichlorohexyl nitrite, 2,2-dichloroheptyl nitrite, 2,2-dichlorooctyl nitrite, 2,2-dichlorononyl nitrite, 2,2-dichlorodecyl nitrite, and the like monochloroalkyl nitrites, their isomeric forms, and the like; nitroalkyl nitrites, such as 2-nitroethyl nitrite, 2-nitropropyl nitrite, 2-nitrobutyl nitrite, 2-nitroamyl nitrite, 2-nitrohexyl nitrite, 2-nitroheptyl nitrite, Z-nitrooctyl nitrite, 2-

nitrononyl nitrite, 2-nitrodecyl nitrite, and their isomeric forms, and the like; aralkyl nitrites, such as benzyl nitrite, 2-methylbenzyl nitrite, 3-methylbenzyl nitrite, 4-methylbenzyl nitrite, Z-ethylbenzyl nitrite, 3-ethylbenzyl nitrite, 4-ethylbenzyl nitrite, Z-propylbenzyl nitrite, 3-propylbenzyl nitrite, 4propylbenzyl nitrite, 2-methyl-3-ethylbenzyl nitrite, 2-methyl-4-ethylbenzyl nitrite, 2-methyl-5- ethylbenzyl nitrite, 2-rnethyl-6-ethylbenzyl nitrite, 3-methyl-4-ethylbenzyl nitrite, 3-methyl-5-ethylbenzyl nitrite, 3- methyl-6-ethylbenzyi nitrite, 4-rnethyi-2-ethylbenzyl nitrite, 4-methyl-3-ethylbenzyl nitrite, 2,3-d-imethylbenzyl nitrite, 2,4-dimethylbenzyl nitrite, 2,5-dimethylbenzyl nitrite, 2,6-dimethylbenzyl nitrite, 3,4-dimethyi'oenzyl nitrite, 3,5-dimethylbenzyl nitrite, and the like; and alkoxyalkyl nitrites, such as Z-methoxyethyl nitrite, 2-ethoxyethyl nitrite, Z-propoxyethyl nitrite, Z-butoxycthyl nitrite, Z-pentoxyethyl nitrite, Z-hexoxyethyl nitrite, Z-heptoxyethyl nitrite, 2-octoxyethyl nitrite, 2-nonoxyethyl nitrite, 2-decoxyethyl nitrite, and their isomeric forms and the like.

Another excellent polymerization activator is carbon disulfide. Silicon halides and organic silicon halides having the general formula:

wherein R is a saturated or unsaturated aliphatic or aromatic hydrocarbon radical containing 1 to 10 carbon atoms, a saturated or unsaturated aliphatic or aromatic halogenated hydrocarbon radical containing 1 to 18 carbon atoms, and X is a halogen, z is an integer from 1 to 4 inclusive, and y is equal to 4-z, wherein R may be similar or dissimilar radicals, may also be employed to activate polymerization of Z-pyrrolidone. Among the silicon halides and organic silicon halides there may be named tetrachlorosilane, alpha,beta dichloroethyltrichlorosilane, bis (chloromethyl) methylchlorosilane, butyitrichlorosilane, chloromethylmethyldichlorosilane, dichloromethy?dimethylchlorosilane, diethyldichlorosilane, dimethyldichlorosilane, diphenyldichlorosilane, ethyltrichlorosilane, methyltrichlorosilane, phenyltrichlorosilane, propyltrichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, the iodoand bromoforms of the above compounds, and many others. The trihalides of phosphorous, aluminum, bismuth and antimony, the tetrahalides of titanium, tin, zirconium and lead, and the pentahalides of antimony and phosphorus are also useful as activators in the polymerization of 2-pyrrolidone. Such compounds include aluminum trichloride, aluminum tribromide, aluminum triiodide, stannic tetrachloride, stannic tetrabromide, lead tetrachloride, zirconium tetrachloride, bismuth trichloride, bismuth tribromide, antimony trichloride, antimony tribromide, antimony triiodide, antimony pentachloride, antimony pentaiodide, antimony pentafluoride, and the like. The phosphorus halides include phosphorus tribromide, phosphorous pentabromide, phosphorus trichloride, phosphorus pentachloride, phosphorous trifiuoride, phosphorus pentafluoride, phosphorus triiodide, and the like. Generally, in the preparation of polypyrrolidone wherein both a catalyst and activator are employed to bring about polymerization, the activator is utilized in a range of 0.0001 to 0.075 chemical equivalents of activator, based upon one mole of Z-pyrrolidone.

The polypyrrolidone soluble in the solvent of the invention is prepared by simple polymerization methods. It can be prepared readily by well-known solution, emulsion, suspension or bulk polymerization procedures. The solution and emulsion polymerizations may be either batch, semi-continuous or continuous methods. When solution polymerization is employed, the monomer is dissolved in a solvent such as 1,4-dioxane, the desired catalyst or activator, or both, added to the solution, and the polymerization carried out under the proper conditions. Well-known solution polymerization apparatus is suitable for preparing the polypyrrolidone described herein. 7 Where either emulsion or suspension polymerization techniques are employed to prepare the polymer, the monomer containing the catalyst is dispersed in a non-solvent, such as petroleum ether, and an emulsifying agent, then added to the dispersion. Subsequently, the desired activator is injected into the mixture and the dispersion is polymerized until the reaction is complete. At this time, suitable coagulant is added to the polymerization mixture in order to precipitate the polymer. A suitable emulsifying agent is sodium lauryl sulfate, and the suitable coagulant is phosphoric acid.

Polypyrrolidone prepared in accordance with the procedures set forth'hereinabove has a melting point of about 260 C. and a specific viscosity of from about 0.2 to 9.4 or more. Specific viscosity as defined in the invention is the specific viscosity at 0.5 percent concentration of the polypyrrolidone in 90 percent formic acid at 25 C. It is thus particularly adapted for the manufacture of shaped articles such as filaments, fibers, films, rods, bristles, and the like. Lower molecular weight polymers prepared in the same manner are suitable for the preparation of coatings or lacquers.

The following examples are intended to illustrate the new compositions of this invention more fully but are not intended to limit the scope of the invention, for it is possible to elfect many modifications therein. In the examples, all parts and percents are by weight unless otherwise indicated.

Example I To a 0.50 gram sample of polypyrrolidone in a 7 mm. ID. glass tube there was added 1.5 grams of distilled water. The tube was sealed and suspended in a stirred oil bath and the temperature gradually raised. The polypyrrolidone began to go into solution at 120 C. and was completely in solution at 128 C. The dope was clear and colorless. On cooling, the polymer reprecipitated at 104 C. The specific viscosity of the recovered polymer was 0.515. A sample of the same polymer that had not been dissolved in water had a specific viscosity of 0.535 (indicating a molecular weight of approximately 9,400). Therefore, no significant degradation occurred. The solution which was made was suitable for spinning fibers by the dry spinning method.

Example 11 To a 0.50 gram sample of polypyrrolidone having a specific viscosity of 1.855 placed in a mm. ID. glass tube there was added grams of water. The tube was sealed and suspended in a stirred oil bath and the temperature gradually raised. Complete dissolution of the sample was not attained at 157 C. due to a small amount of foreign material. Otherwise, the dope was clear and colorless. On cooling, the polymer reprecipitated at 130 C. The specific viscosity of the recovered polymer showed no significant degradation. The solution which was made was suitable for spinning fibers by the dry spinning method.

Example II! To a 0.50 gram sample of polypyrrolidonc having a specific viscosity of 0.833 (indicating a molecular weight of approximately 17,000) placed in a 10 mm. ID. glass tube there was added 20 grams of water. The tube was sealed and suspended in a stirred oil bath and the temperature gradually raised. Complete dissolution of the sample was attained at 135 C. The dope was clear and colorless. On cooling, the polymer reprecipitated at 125 C. The specific viscosity of the recovered polymer showed no significant degradation. The solution which was made was suitable for spinning fibers by the dry spinning method.

Example IV To a 0.50 gram sample of polypyrrolidone having a Example V To, 0.25 gram of polypyrrolidone in a 7 mm. ID. glass tube there was added 2.0 grams of distilled water. The tube was sealed and suspended in a stirred oil bath and the temperature raised approximately 2 C. per minute. The polymer started to turn clear, indicating the beginning of dissolution at 135 C. Dissolution was complete at 165 C. on slow cooling the polymer started precipitating at 130 C. The specific viscosity of the recovered polymer showed no significant degradation.

The polymer used in this example had a specific viscosity of 9.406, an intrinsic viscosity of 8.5, and a weight average molecular weight, as determined by conventional light scattering techniques on solutions of the polymer containing up to 1.2 grams per liter of the polymer in a solvent consisting of percent formic acid containing 0.5 mols of sodium formate per liter, of 4.5 10 The solution which was made was suitable for spinning fibers by the dry spinning method.

Example V1 0.5 gram of polypyrrolidone having a specific viscosity of 0.205 (indicating a molecular weight of approximately 3,000) was put in a 7 mm. ID. glass tube and then 1.0 gram of water was added. The tube was sealed and suspended in a stirred oil bath and the temperature of the bath was raised approximately 2 C. per minute. The polymer started dissolving at 120 C. and dissolution was complete at 138 C. On slow cooling the polymer started precipitating at C. The specific viscosity of the recovered polymer showed no significant degradation. The solution which was made was suitable for preparation of coatings, films, etc.

Polypyrrolidone prepared with other catalysts and activators and having varying molecular weights and viscosity values give like results when dissolved in the solvent of this invention. 7

The new compositions of this invention present many advantages. Water, as is well known, is inexpensive and easily obtained.

Polymeric solutions made with the new solvent of this invention are clear and colorless and products or shaped articles prepared therefrom exhibit good color characteristics. Furthermore, in preparing a solution of polypyrrolidone the new solvent of this invention may be employed without elaborate safety precautions and it has no eifect upon the desirable chemical and physical properties of the product dissolved therein. Numerous other advantages of the composition of this invention will be readily apparent to those skilled in the art.

It will be understood to those skilled in the art that many apparently widely different embodiments of this invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A solution consisting of polypyrrolidone dissolved in water superheated to a temperature range of C. to C.

2. A solution consisting of five to thirty-five percent polypyrrolidone, based on the total weight of the com- 7 position, dissolved in water, superheated to a temperature range of from 120 C. to 180 C.

3. A solution consisting of polypyrrolidone having a specific viscosity between the range of 0.2 and 9.1, dissolved in water, superheated to a temperature range of 120 to 180 C.

4. A solution consisting of to 35 percent polypyrrolidone, based on the total weight of the solution, having a specific viscosity between the range of 0.2 to 9.1, dissolved in water superheated to a temperature range of from 120 C. to 180 C.

5. A new fiber formingsolution consisting of 5 to 35 percent polypyrrolidone, based on the total weight of the solution, having a specific viscosity between the range of 0.5 to 9.4, dissolved in water superheated to a temperature range from 120 C. to 180 C.

6. A process for preparing a new composition of matter consisting of mixing polypyrrolidone in Water, sealing in a tube, and heating the mixture to a temperature within arange of'120 C. to 160 C.

7. A process as set forth in claim 6 in which the polypyrrolidone comprises 5 to percent based on the total weight of the composition.

8. A process as set forth in claim 6 in which the polypyrrolidone has a specific viscosity between the range of 0.2 and 9.4.

'9. A process as set forth in claim 6 in which the polypyrrolidone comprises a range of 5 to 35 percent based on the total weight of the composition and has a specific viscosity between the range of 0.2 and 9.4.

References Cited in the file of this patent UNITED STATES PATENTS 2,638,463 Ney et al May 12, 1953 2,980,641 Cox Apr. 18, 1961 3,003,984 Black Oct. 10, 1961 3,003,985 Black Oct. 10, 1961 

1. A SOLUTION CONSISTING OF POLYPYRROLIDONE DISSOLVED IN WATER SUPERHEATED TO A TEMPERATURE RANGE OF 120*C. TO 180*C. 